This invention deals generally with vehicle towing and more specifically with a towing plate for receiving a winch line hook and adjusting the length of the chain that is attached to the vehicle.
Although many people have had the distressing experience of having a vehicle they were driving require towing, few understand the complications of accomplishing that task. Even with the use of so-called xe2x80x9croll-back trucksxe2x80x9d it is necessary to hook chains to the disabled vehicle, and those chains should be attached to or encircle more than a single point on the disabled vehicle, even though the tow vehicle or tie down point on the roll-back platform uses only a single winch line. This usually involves a set of chains which is more complicated than the layperson appreciates.
The prior art means for adapting a winch line from the towing vehicle or roll-back platform to the multiple attachment points on the disabled vehicle is called a xe2x80x9cVxe2x80x9d chain assembly. This configuration of chains involves an oblong center ring to which two separate lengths of chain are permanently attached. Small grab hooks are also attached to the same end link of each chain which is attached to the center ring, and a cluster of differently shaped fixtures are permanently attached to the chains at the ends of the chains remote from the center ring. The cluster of fixtures includes xe2x80x9cJxe2x80x9d hooks, xe2x80x9cRxe2x80x9d hooks, and xe2x80x9cTxe2x80x9d hooks all of which are conventional devices well known in the art. In use, the winch line from the tow truck or the tie-down platform is attached to the center ring, and the other two chains are wrapped around the disabled vehicle attachment points, or the hooks are attached directly to the disabled vehicle. In either case, the grab hooks near the center ring are attached to selected links of the chains to adjust the length of the segments of the chains.
Although such xe2x80x9cVxe2x80x9d chain assemblies work satisfactorily for the tasks of towing or tying down a disabled vehicle, those who regularly use them have come to appreciate their limitations. First of all, the xe2x80x9cVxe2x80x9d chain assemblies are very heavy. Furthermore, the inclusion of the grab hooks in the assembly make it very likely that the assembly will become severely tangled upon itself anytime it is stored.
It would be very beneficial to have available an adapter assembly which has less weight than the typical xe2x80x9cVxe2x80x9d chain assembly and which would not require grab hooks to be dealt with at all times.
The present invention reduces the weight of tow chain assemblies and reduces the likelihood of tangling. The invention is a towing plate which functions both as a center ring for attachment of the tow vehicle""s winch line and as a device for adjusting the length of the xe2x80x9cVxe2x80x9d chains to be attached to the disabled vehicle. Actually, the towing plate uses only a single chain to serve as both xe2x80x9cVxe2x80x9d chains and eliminates the need for the conventional grab hooks. Thus, the single chain of the assembly can be stored like any other individual chain with less chance of tangling. Moreover, even if the single chain does become tangled upon itself, it is much easier to untangle because it is merely a single chain with only end hooks.
These benefits are accomplished by the design of the towing plate of the invention. The towing plate is somewhat longer than it is wide and has three holes that are balanced across the centerline of the long dimension of the plate. The shape and dimensions of the plate are essentially determined by maintaining a specified minimum width of material around each hole. In the preferred embodiment, for a xe2x85x9c inch thick plate of 4130/4140 steel, the width of material around each hole is approximately one half inch, and this design of the plate safely yields a rated 4200 pounds towing capacity. The dimension for the width of material around each hole can actually be determined by conventional calculations for any material, plate thickness, and required towing capacity.
In the preferred embodiment, one large pear shaped hole is centered between the sides of the plate with the large end of the hole near the plate""s edge at one end of the centerline of the plate. Two smaller oblong holes with rounded ends are located near the narrow end of the larger hole in a configuration that is balanced relative to the centerline of the plate, and with the long sides of the smaller holes oriented at equal but opposite angles to the centerline of the plate. The smaller holes have slots extending away from the large hole from their edges most remote from the large hole, with the slots oriented at an angle to the centerline of the plate, so that the combination of the smaller holes and the slots take on the shape of the heads of golf clubs.
The size of the large hole is determined by the requirement that the links and the hook of the tow chain must freely pass through it. The curve of the large hole nearest to the edge of the plate is rounded in the conventional manner so that it accepts a conventional hook.
The sizes of the two smaller holes are determined by the requirement that while the links of the chain must freely pass through the holes, the dimensions of the holes must be too small to permit the hooks on the chain to pass through the holes. This structure is attained by putting the chain through both smaller holes before attaching the hook or cluster of hooks to at least one end of the chain.
The slots extending from the smaller holes are conventional chain locking slots. That is, the slots are dimensioned to permit individual links of the chain to slide into them when the link""s planar orientation is parallel to the slot and to prevent adjacent links oriented in different planes from moving through the slot. The length of the slot is selected to maintain the link within the slot. An important feature of the smaller holes is that each has a slot and that the slots extend from the two holes at an angle to each other. This angle causes the remote ends of the chain locked into the slots to deviate from each other as is desirable for attachment to the separated points on the disabled vehicle to which the remote ends of the chain are to be attached.
The present invention therefore furnishes a towing plate which reduces the weight of the towing chain assembly and reduces the tangling when the assembly is stored, while maintaining ease of use and full safety.